A friend just sent me a resource that's free for October that helps writers and designers keep track of pretty much every detail of the world they're creating.
Everything from that random NPC's favorite food to the motto of the town where your characters buy items can be managed.
After playing around with it for a few minutes, it's amazing all the details you can enter in. And now, I don't have to remember which random notebook I jotted stuff down in.
Check it out: http://www.notebook.ai/